Emerging Applications for Titanium-Based Alloys

Future growth in industrial and marine applications for titanium-based alloys will be predicated more on the development of new markets rather than the expansion of existing markets. Many new applications will utilize the high strength and low density of titanium as well as its resistance to corrosion and erosion. Effective use of alloying elements will allow the usage of titanium in a wider range of reducing environments.

Important new applications for titanium-based alloys include flue gas desulfurization (FGD) and other scrubber systems, sour gas and deep well services, and various marine applications.

Numerous end-users have experienced corrosion problems with various stainless steels, nickel-based alloys and nonmetallic materials in FGD systems. Laboratory tests show that various grades of titanium, especially Grade 12 (Ti-0.3Mo-0.8Ni), offers excellent corrosion resistance in scrubber environments even when fluorides are present. The presence of fly ash in the solution improves its corrosion resistance even further due most likely to the presence of multivalent metallic cations.

Laboratory tests reported in this work demonstrate that the corrosion resistance of Grade 12 is superior to that of stainless steels and nickel-based alloys commonly used in FGD systems.

Sour gas and deep well environments contain exceptionally corrosive fluids at high temperatures and pressures. Corrosion resistance of the titanium-based alloys in deep wells has been proven by both “in service” and laboratory experience. Alloys like Ti-6Al-4V are utilized currently in casings and springs for logging equipment which operate in hostile sour gas environments. Laboratory tests conducted by RMI, Battelle, and Climax Molybdenum demonstrate excellent resistance of beta titanium alloys to corrosion and stress corrosion cracking from acidified sodium chloride solutions containing carbon dioxide and hydrogen sulfide at temperatures reaching 230°C (450°F). Titanium-based alloys also offer several unique properties which increase performance and life span of equipment in this service. Beta titanium alloys like Ti-15Mo-5Zr-3Al with tensile strengths in excess of 1200 MPa (175 000 psi) combine high strength and low density, allowing the weight of components like tubestrings to be half that of nickel-based alloys. Titanium-based alloy equipment also offers superior dependability and performance in tough marine service. Alloys like Ti-6Al-2Cb-1Ta-1Mo and Ti-6Al-4V are being evaluated for pressure vessel and high-stress applications. Several grades of titanium like Ti-3Al-2.5V and Grade 1 will be used in heat transfer and pipe systems for surface and subsurface ships. Titanium is being utilized also for major structure components of military vessels in order to optimize performance.